~(17,18)O(α,n) Evaluated Cross Sections to Improve National Security Applications

摘要

The R-matrix SAMMY implementation was applied usingthe Reich-Moore approximation to determine a consistent,albeit preliminary, set of resonance parameters and relatedcovariance information for α+~(17,18)O in the energy range up to5 MeV. The resonance analysis within the R-matrix formalismallowed to estimate the partial contributions of the (α,n) crosssections to each excited states on the basis of convoluted datasets and, partially, on HF calculations. In this regard the needof experimental data with explicit information on the partialcross sections is recommended. Since in SOURCES-4C thereare predefined branching ratios for each excited states, additionalwork is needed to test the impact of the newly evaluatedpartial cross sections for each excited state on the emergingneutron spectra. Analyses to determine the correct ratio of thepartial cross sections to the total (α,n) cross sections in orderto improve the agreement with the neutron spectra are still inprogress.This work was motivated by (1) the need to provide evaluateddata to improve the state of the art in modeling neutronemission processes essential for nuclear material verificationand (2) to estimate uncertainty in the neutron generation rates.Future work will finalize and formalize the evaluationwork on ~(17,18)O(α,n) cross sections by including the evaluatedset of resonance parameters and related covariance informationin future releases of the charged-particle ENDF/B-Ⅷ sublibrary.